Projection system and projector

ABSTRACT

A projection system includes a first optical system and a second optical system including an optical element and a reflector and disposed at the enlargement side of the first optical system. The optical element has a reflection surface, a first transmissive surface disposed at the enlargement side of the reflection surface, and a second transmissive surface disposed at the enlargement side of the first transmissive surface. The reflector is disposed at the enlargement side of the reflection surface and at the reduction side of the first transmissive surface. The reflector is disposed between the optical element and the first optical system in the direction along a first optical axis of the first optical system.

The present application is based on, and claims priority from JPApplication Serial Number 2020-008952, filed Jan. 23, 2020, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a projection system and a projector.

2. Related Art

JP-A-2010-20344 describes a projector that enlarges and projects aprojection image formed by an image formation section via a projectionsystem. The projection system described in JP-A-2010-20344 is formed ofa first optical system and a second optical system sequentially arrangedfrom the reduction side toward the enlargement side. The first opticalsystem includes a refractive optical system. The second optical systemis formed of a reflection mirror having a concave reflection surface.The image formation section includes a light source and a light valve.The image formation section forms a projection image in thereduction-side image formation plane of the projection system. Theprojection system forms an intermediate image in a position between thefirst optical system and the reflection surface and projects a finalimage on a screen disposed in the enlargement-side image formation planeof the projection system.

The projection system and the projector are required to have a shorterprojection distance. An attempt to further shorten the projectiondistance in the configuration using the projection system described inJP-A-2010-20344, however, causes a problem of a difficulty in designingthe projection system.

SUMMARY

To solve the problem described above, a projection system according toan aspect of the present disclosure include a first optical system and asecond optical system including an optical element and a reflector anddisposed at an enlargement side of the first optical system. The opticalelement has a reflection surface, a first transmissive surface disposedat the enlargement side of the reflection surface, and a secondtransmissive surface disposed at the enlargement side of the firsttransmissive surface. The reflector is disposed at the enlargement sideof the reflection surface and at a reduction side of the firsttransmissive surface. The reflector is disposed between the opticalelement and the first optical system in a direction along a firstoptical axis of the first optical system.

A projector according to another aspect of the present disclosureincludes the projection system described above and an image formationsection that forms a projection image in a reduction-side imageformation plane of the projection system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a projector including aprojection system.

FIG. 2 is a light ray diagram diagrammatically showing the entireprojection system according to Example 1.

FIG. 3 is a light ray diagram of the projection system according toExample 1.

FIG. 4 is a light ray diagram of a second optical system of theprojection system according to Example 1.

FIG. 5 shows the enlargement-side MTF of the projection system accordingto Example 1.

FIG. 6 is a light ray diagram diagrammatically showing the entireprojection system according to Example 2.

FIG. 7 is a light ray diagram of the projection system according toExample 2.

FIG. 8 is a light ray diagram of the second optical system of theprojection system according to Example 2.

FIG. 9 shows the enlargement-side MTF of the projection system accordingto Example 2.

FIG. 10 is a light ray diagram diagrammatically showing the entireprojection system according to Example 3.

FIG. 11 is a light ray diagram of the projection system according toExample 3.

FIG. 12 is a light ray diagram of the second optical system of theprojection system according to Example 3.

FIG. 13 shows the enlargement-side MTF of the projection systemaccording to Example 3.

FIG. 14 is a light ray diagram diagrammatically showing the entireprojection system according to Example 4.

FIG. 15 is a light ray diagram of the projection system according toExample 4.

FIG. 16 is a light ray diagram of the second optical system of theprojection system according to Example 4.

FIG. 17 shows the enlargement-side MTF of the projection systemaccording to Example 4.

FIG. 18 is a light ray diagram diagrammatically showing the entireprojection system according to Example 5.

FIG. 19 is a light ray diagram of the projection system according toExample 5.

FIG. 20 is a light ray diagram of the second optical system of theprojection system according to Example 5.

FIG. 21 shows the enlargement-side MTF of the projection systemaccording to Example 5.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A projection system according to an embodiment of the present disclosureand a projector including the projection system will be described belowin detail with reference to the drawings.

Projector

FIG. 1 is a schematic configuration diagram of a projector including aprojection system 3 according to the present disclosure. A projector 1includes an image formation section 2, which generates a projectionimage to be projected on a screen S, the projection system 3, whichenlarges the projection image and projects the enlarged image on thescreen S, and a controller 4, which controls the action of the imageformation section 2, as shown in FIG. 1 .

Image Generation Optical System and Controller

The image formation section 2 includes alight source 10, a first opticalintegration lens 11, a second optical integration lens 12, apolarization converter 13, and a superimposing lens 14. The light source10 is formed, for example, of an ultrahigh-pressure mercury lamp orasolid-state light source. The first optical integration lens 11 and thesecond optical integration lens 12 each include a plurality of lenselements arranged in an array. The first optical integration lens 11divides the light flux from the light source 10 into a plurality oflight fluxes. The lens elements of the first optical integration lens 11focus the light flux from the light source 10 in the vicinity of thelens elements of the second optical integration lens 12.

The polarization converter 13 converts the light via the second opticalintegration lens 12 into predetermined linearly polarized light. Thesuperimposing lens 14 superimposes images of the lens elements of thefirst optical integration lens 11 on one another in a display region ofeach of liquid crystal panels 18R, 18G, and 18B, which will be describedlater, via the second optical integration lens 12.

The image formation section 2 further includes a first dichroic mirror15, a reflection mirror 16, a field lens 17R, and the liquid crystalpanel 18R. The first dichroic mirror 15 reflects R light, which is partof the light rays incident via the superimposing lens 14, and transmitsG light and B light, which are part of the light rays incident via thesuperimposing lens 14. The R light reflected off the first dichroicmirror 15 travels via the reflection mirror 16 and the field lens 17Rand is incident on the liquid crystal panel 18R. The liquid crystalpanel 18R is a light modulator. The liquid crystal panel 18R modulatesthe R light in accordance with an image signal to form a red projectionimage.

The image formation section 2 further includes a second dichroic mirror21, a field lens 17G, and the liquid crystal panel 18G. The seconddichroic mirror 21 reflects the G light, which is part of the light raysvia the first dichroic mirror 15, and transmits the B light, which ispart of the light rays via the first dichroic mirror 15. The G lightreflected off the second dichroic mirror 21 passes through the fieldlens 17G and is incident on the liquid crystal panel 18G. The liquidcrystal panel 18G is a light modulator. The liquid crystal panel 18Gmodulates the G light in accordance with an image signal to form a greenprojection image.

The image formation section 2 further includes a relay lens 22, areflection mirror 23, a relay lens 24, a reflection mirror 25, a fieldlens 17B, and the liquid crystal panel 18B. The B light having passedthrough the second dichroic mirror 21 travels via the relay lens 22, thereflection mirror 23, the relay lens 24, the reflection mirror 25, andthe field lens 17B and is incident on the liquid crystal panel 18B. Theliquid crystal panel 18B is a light modulator. The liquid crystal panel18B modulates the B light in accordance with an image signal to form ablue projection image.

The liquid crystal panels 18R, 18G, and 18B surround a cross dichroicprism 19 in such a way that the liquid crystal panels 18R, 18G, and 18Bface three sides of the cross dichroic prism 19. The cross dichroicprism 19, which is a prism for light combination, produces a projectionimage that is the combination of the light modulated by the liquidcrystal panel 18R, the light modulated by the liquid crystal panel 18G,and the light modulated by the liquid crystal panel 18B.

The cross dichroic prism 19 forms part of the projection system 3. Theprojection system 3 enlarges and projects the projection images (imagesformed by liquid crystal panels 18R, 18G, and 18B) combined by the crossdichroic prism 19 on the screen S. The screen S is the enlargement-sideimage formation plane of the projection system 3.

The controller 4 includes an image processor 6, to which an externalimage signal, such as a video signal, is inputted, and a display driver7, which drives the liquid crystal panels 18R, 18G, and 18B based onimage signals outputted from the image processor 6.

The image processor 6 converts the image signal inputted from anexternal apparatus into image signals each containing grayscales andother factors of the corresponding color. The display driver 7 operatesthe liquid crystal panels 18R, 18G, and 18B based on the colorprojection image signals outputted from the image processor 6. The imageprocessor 6 thus causes the liquid crystal panels 18R, 18G, and 18B todisplay projection images corresponding to the image signals.

Projection System

The projection system 3 will next be described. Examples 1 to 5 will bedescribed below as examples of the configuration of the projectionsystem 3 incorporated in the projector 1. In the light ray diagrams ofthe projection system according to Examples 1 to 5, the liquid crystalpanels 18R, 18G, and 18B are referred to as liquid crystal panels 18.

Example 1

FIG. 2 is a light ray diagram diagrammatically showing the entireprojection system according to Example 1. FIG. 2 diagrammatically showslight fluxes F1 to F4, which exit out of a projection system 3Aaccording to the present example and reach the screen S. The light fluxF1 is a light flux that reaches a smallest image height position. Thelight flux F4 is a light flux that reaches a largest image heightposition. The light fluxes F2 and F3 are light fluxes that reachpositions between the position that the light flux F1 reaches and theposition that the light flux F4 reaches. FIG. 3 is a light ray diagramof the projection system 3A according to Example 1. FIG. 4 is a lightray diagram of a second optical system in Example 1.

The projection system 3A according to the present example includes afirst optical system 31 and a second optical system 32 sequentiallyarranged from the reduction side toward the enlargement side, as shownin FIG. 3 . The first optical system 31 is a refractive optical systemincluding a plurality of lenses. The second optical system 32 includesan optical element 33 and a reflector 34. The optical element 33 has areflection surface 41, a first transmissive surface 42, and a secondtransmissive surface 43. The reflector 34 is a flat mirror. In thesecond optical system 32, the reflection surface 41, the reflector 34,the first transmissive surface 42, and the second transmissive surface43 are located in the presented order along the light travelingdirection from the reduction side toward the enlargement side.

The liquid crystal panels 18 of the image formation section 2 aredisposed in the reduction-side image formation plane of the projectionsystem 3A. The liquid crystal panels 18 form the projection images atone side of a first optical axis N of the first optical system 31 in aplane perpendicular to the first optical axis N. The screen S isdisposed in the enlargement-side image formation plane of the projectionsystem. An intermediate image 35 conjugate with the reduction-side imageformation plane is formed between the first optical system 31 and thereflection surface 41 of the optical element 33. The intermediate image35 is conjugate also with the enlargement-side image formation plane.The intermediate image 35 is formed at the side opposite the screen Swith respect to the first optical axis N of the first optical system 31.

In the following description, three axes perpendicular to one anotherare called axes X, Y, and Z for convenience. The width direction of thescreen S, which is the enlargement-side image formation plane, is calledan axis-X direction, the upward/downward direction of the screen S iscalled an axis-Y direction, and the direction perpendicular to thescreen S is called an axis-Z direction. The plane containing the firstoptical axis N of the first optical system 31 and a second optical axisM of the reflection surfaces 41 of the optical element 33 is called aplane YZ.

The first optical axis N of the first optical system 31 extends in theaxis-Z direction in the present example. FIGS. 2, 3, and 4 are each alight ray diagram in the plane YZ. The liquid crystal panels 18 form theprojection images at an upper side Y1 of the first optical axis N of thefirst optical system 31. The intermediate image 35 is formed at a lowerside Y2 of the first optical axis N of the first optical system 31. Thescreen S is disposed at the upper side Y1 of the first optical axis N ofthe first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15lenses L1 to L15, as shown in FIG. 3 . The lenses L1 to L15 are arrangedin the presented order from the reduction side toward the enlargementside. In the present example, the lenses L2 and L3 are bonded to eachother into a first doublet L21. The lenses L4 and L5 are bonded to eachother into a second doublet L22. The lenses L11 and L12 are bonded toeach other into a third doublet L23. The lenses L13 and L14 are bondedto each other into a fourth doublet L24. An aperture O is disposedbetween the lens L7 and the lens L8.

The optical element 33 includes a meniscus lens 36, which has a convexshape at the enlargement side, and a reflection coating layer 37, whichis provided on part of the reduction-side surface of the meniscus lens36. The reflection surface 41 of the optical element 33 is thereflection coating layer 37. The optical element 33 is designed by usingthe second optical axis M of the reflection surface 41 as the axis inthe design stage. In other words, the second optical axis M is thedesign-stage optical axis of the reflection surface 41, the firsttransmissive surface 42, and the second transmissive surface 43. Thesecond optical axis M of the reflection surface 41 coincides with thefirst optical axis N of the first optical system 31, as shown in FIG. 4. The second optical axis M of the reflection surface 41 thereforeextends along the axis Z. The reflection surface 41 is located at thelower side Y2 of the second optical axis M. The first transmissivesurface 42 and the second transmissive surface 43 are located at theupper side Y1 of the second optical axis M. The reflection surface 41,the first transmissive surface 42, and the second transmissive surface43 of the optical element 33 are each an aspheric surface. The asphericsurfaces are each a free-form surface in some cases. Also in this case,the free-form surfaces are designed by using the second optical axis Mas the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of thereflection surface 41. The reflector 34 is located at the upper side Y1of the second optical axis M of the reflection surface 41. The reflector34 is shifted from the optical element 33 toward the first opticalsystem 31 in the direction along the second optical axis M of thereflection surface 41.

A pupil P of the second optical system 32 is located inside the secondoptical system 32. The pupil P of the second optical system 32 in theplane YZ is defined by the line that connects an upper intersection 53,where an upper peripheral light ray 51 a of an upper end light flux 51passing through the axis-Y-direction upper end of an effective light rayrange 50 of the second transmissive surface 43 and an upper peripherallight ray 52 a of a lower end light flux 52 passing through theaxis-Y-direction lower end of the effective light ray range 50 intersecteach other in the plane YZ, to a lower intersection 54, where a lowerperipheral light ray 51 b of the upper end light flux 51 and a lowerperipheral light ray 52 b of the lower end light flux 52 intersect eachother in the plane YZ. The pupil P is formed between the reflector 34and the second transmissive surface 43. The pupil P inclines withrespect to an imaginary vertical line V perpendicular to the secondoptical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3A are listed below. Thesurfaces of the lenses are numbered sequentially from the reduction sidetoward the enlargement side. Reference characters are given to thelenses, the reflection surface, the reflector, the first transmissivesurface, and the second transmissive surface. Data labeled with asurface number that does not correspond to any of the lenses, thereflection surface, the reflector, the first transmissive surface, andthe second transmissive surface is dummy data. Reference character Rdenotes the radius of curvature. Reference character D denotes the axialinter-surface distance. Reference character C denotes the apertureradius. Reference characters R, D, and C are each expressed inmillimeters.

Reference Surface Refraction/ character number Shape R D Glass materialreflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity25.9100 SBSL7_OHARA Refraction 13.3059 3 Spherical Infinity 0.0000Refraction 16.1679 L1 4 Spherical 27.2275 9.6207 SFPL51_OHARA Refraction17.2029 5 Spherical −96.6617 0.2000 Refraction 16.8825 L2 6 Spherical29.0138 7.7348 SFSL5 OHARA Refraction 14.8572 L3 7 Spherical −60.78681.2000 STIH6_OHARA Refraction 14.0000 8 Spherical 46.8651 0.2000Refraction 12.8622 L4 9 Spherical 20.0287 9.3478 SBSL7_OHARA Refraction12.3016 L5 10 Spherical −22.8718 1.2000 TAFD25_HOYA Refraction 11.559611 Spherical 190.2895 0.4397 Refraction 10.9652 L6 12 Aspheric 41.85371.2000 LBAL35_OHARA Refraction 10.8731 13 Aspheric 21.5006 0.2000Refraction 10.4882 L7 14 Spherical 19.3529 7.5650 SFSL5_OHARA Refraction10.5273 15 Spherical 62.6402 2.2349 Refraction 9.5673 O 16 SphericalInfinity 0.4040 Refraction 9.2670 L8 17 Spherical 29.3227 4.6147STIH53_OHARA Refraction 10.2078 18 Spherical −68.0342 3.3630 Refraction10.2526 L9 19 Aspheric −87.2281 5.6840 LLAM60_OHARA Refraction 10.001820 Aspheric 20.5876 4.2883 Refraction 11.2693 21 Spherical Infinity0.2988 Refraction 12.5570 L10 22 Spherical 40.1891 3.9043 STIM22_OHARARefraction 15.2007 23 Spherical 112.0759 20.7200 Refraction 15.5454 L1124 Spherical 62.0827 22.5281 STIM2_OHARA Refraction 26.0000 L12 25Spherical −30.5918 1.2000 STIH6_OHARA Refraction 26.1404 26 Spherical138.3228 0.2000 Refraction 30.0612 L13 27 Spherical 105.8154 15.0227STIL25_OHARA Refraction 31.1823 L14 28 Spherical −64.8091 1.3233STIH6_OHARA Refraction 31.6527 29 Spherical −64.5253 0.2000 Refraction31.9494 L15 30 Aspheric −338.6023 2.2476 ‘Z-E48R’ Refraction 32.5943 31Aspheric 45.8885 13.3862 Refraction 32.0721 32 Spherical Infinity16.7098 Refraction 31.7316 33 Spherical Infinity 39.3523 Refraction30.1083 41 34 Aspheric 46.4264 −39.3523 Reflection 37.4512 34 35Spherical Infinity 39.3523 Reflection 38.7046 42 36 Aspheric −50.25031.2000 ‘Z-E48R’ Refraction 39.8994 43 37 Aspheric −162.2411 0.0000Refraction 58.4637 38 Spherical Infinity 439.5080 Refraction 158.9958 S39 Spherical Infinity 0.0000 Refraction 1487.1211

The aspheric coefficients of each of the aspheric surfaces are listedbelow.

Surface number S12 S13 S19 Radius of 41.85372823 21.50057506−87.22813862 curvature in axis-Y direction Conic constant  1.568 −1.3 −1 (k) Fourth-order −1.92815E−04 −1.48851E−04  −7.47776E−05 coefficient(A) Sixth-order  1.53921E−06  1.63590E−06  −7.57612E−09 coefficient (B)Eighth-order −6.56218E−09 −7.90242E−09  −1.24201E−10 coefficient (C)Tenth-order  1.33383E−11  1.76919E−11 coefficient (D) Twelfth-ordercoefficient (E) Fourteenth-order coefficient (F)

Surface number S20 S30 S31 Radius of 20.58762759 −338.602294545.88845982 curvature in axis-Y direction Conic constant −0.88   90  0(k) Fourth-order −3.30064E−05    2.13930E−05 −1.77739E−06 coefficient(A) Sixth-order  6.74245E−08   −1.77680E−08  1.39563E−08 coefficient (B)Eighth-order −1.14226E−10    1.22895E−11 −2.21256E−11 coefficient (C)Tenth-order   −1.11769E−14  5.46695E−15 coefficient (D) Twelfth-order   7.16104E−18  4.41203E−18 coefficient (E) Fourteenth-order  −2.09326E−21 −2.25037E−21 coefficient (F)

Surface number S34 S36 S37 Radius of −46.42641713 −50.2503134−162.2411346 curvature in axis-Y direction Conic constant  −1  0.55805156    6.222885555 (k) Fourth-order   7.13212E−07  −1.95028E−06  −2.69488E−06 coefficient (A) Sixth-order  −5.94905E−10  −1.37400E−09   6.44559E−10 coefficient (B) Eighth-order   1.93757E−13  −4.89909E−14  −7.82591E−14 coefficient (C) Tenth-order   7.20821E−18 coefficient (D)Twelfth-order  −4.35422E−20 coefficient (E) Fourteenth-order  1.23785E−23 coefficient (F)

A maximum object height, the numerical aperture, a mirror radius, a lensoverall length, and TR of the projection system 3A are as follows: Themaximum object height is the dimension from the first optical axis N ofthe projection system 3A to the farthest point therefrom in an imageformation region of the surface of each of the liquid crystal panels 18.The maximum object height is expressed in millimeters. The numericalaperture is abbreviated to NA. The mirror radius is the radius of thefirst reflection surface in millimeters. The final lens radius is thelens radius of the second transmissive surface in millimeters. The lensoverall length of the projection system 3A is the distance inmillimeters from the liquid crystal panels 18 to the second transmissivesurface in the axis-Z direction. TR stands for a throw ratio and is thequotient of the operation of dividing the projection distance by theaxis-X-direction dimension of a projection image projected on the screenS.

Maximum object height 11.7 NA 0.3125 Mirror radius 37.5 Final lensradius 58.5 Lens overall length 232 TR (0.59″ WXGA) 0.27

Effects and Advantages

The projection system 3A according to the present example includes thefirst optical system 31 and the second optical system 32 sequentiallyarranged from the reduction side toward the enlargement side. The secondoptical system 32 in the projection system 3A includes the opticalelement 33, which has the reflection surface 41, the first transmissivesurface 42, and the second transmissive surface 43, and the reflector34. The reflection surface 41, the reflector 34, the first transmissivesurface 42, and the second transmissive surface 43 are located in thepresented order along the light traveling direction from the reductionside toward the enlargement side. The reflector 34 is located betweenthe optical element 33 and the first optical system 31 in the directionalong the first optical axis N of the first optical system 31.

In the projection system 3A according to the present example, the firsttransmissive surface 42 and the second transmissive surface 37 canrefract the light flux reflected off the reflection surface 41 and thereflector 34 in the second optical system 32. The projection distance ofthe projection system is therefore readily shortened as compared with acase where the second optical system has only the reflection surface. Inother words, the projection system 3A according to the present examplecan have a short focal length as compared with the case where the secondoptical system has only the reflection surface.

The projection system 3A according to the present example, whichincludes the reflector 34, can output the light flux having exited outof the second optical system 32 toward the side opposite the firstoptical system 31 in the axis-Y direction. The light flux that exits outof the second optical system 32 is therefore readily oriented in adirection in which the light flux does not interfere with the firstoptical system 31.

The single optical element 33 has the reflection surface 41, the firsttransmissive surface 42, and the second transmissive surface 43. Thereflection surface, the first transmissive surface, and the secondtransmissive surface are therefore disposed with improved precision ascompared, for example, with a case where the reflection surface isprovided on a member different from the optical element having the firsttransmissive surface and the second transmissive surface.

In the present example, the reflection surface 41 is a concave curvedsurface. The projection system can therefore have a short focal length.

Further, in the present example, the optical element 33 has the convexsecond transmissive surface 43 protruding toward the enlargement side.An increase in the size of the reflection surface 41, which is locatedat the enlargement side of the intermediate image 35, can therefore besuppressed even when the projection distance is shortened. That is, thesecond transmissive surface 43 can refract the light flux and cantherefore suppress inclination of the intermediate image 35, which isconjugate with the screen S, with respect to the second optical axis Mof the reflection surface 41 and the resultant increase in the size ofthe intermediate image 35. An increase in the size of the reflectionsurface 41, which is located at the enlargement side of the intermediateimage 35, can therefore be suppressed.

Moreover, in the present example, the optical element 33 has the convexfirst transmissive surface 42 protruding toward the enlargement side. Anincrease in the size of the reflection surface 41, which is located atthe enlargement side of the intermediate image 35, is therefore readilysuppressed even when the projection distance is shortened. That is, thefirst transmissive surface 42 can refract the light flux and cantherefore suppress inclination of the intermediate image 35, which isconjugate with the screen S, with respect to the second optical axis Mof the reflection surface 41 and the resultant increase in the size ofthe intermediate image 35. An increase in the size of the reflectionsurface 41, which is located at the enlargement side of the intermediateimage 35, can therefore be suppressed.

In the optical element 33 in the present example, the reflection surface41, the first transmissive surface 42, and the second transmissivesurface 43, which are located at the enlargement side of theintermediate image 35, are each an aspheric surface. Occurrence ofaberrations is therefore readily suppressed in the enlargement-sideimage formation plane.

Further, the pupil P of the second optical system 32 inclines withrespect to the imaginary vertical line V perpendicular to the secondoptical axis M of the reflection surface 41. A decrease in the amount oflight at a periphery of the screen S that is the periphery at the upperside Y1 can therefore be suppressed as compared with a case where thepupil P of the second optical system 32 is parallel to the imaginaryvertical line V. That is, in the configuration in which the pupil Pinclines with respect to the imaginary vertical line V perpendicular tothe second optical axis M, the amount of light flux F1, which reachesthe upper portion of the screen S, increases as compared with the casewhere the pupil P is parallel to the imaginary vertical line V. Further,when the amount of light flux F1, which reaches the upper portion of thescreen S, increases, the difference in the amount of light between thelight flux F1 and the light flux F3, which reaches the lower portion ofthe screen S decreases. A decrease in the amount of light at the upperperiphery of the screen S as compared with that at the lower peripheryof the screen S can therefore be suppressed.

FIG. 5 shows the enlargement-side MTF of the projection system 3A. Thehorizontal axis of FIG. 5 , which shows the MTF, represents the spatialfrequency. The vertical axis of FIG. 5 represents a contrastreproduction ratio. In FIG. 5 , the black graphs represent tangentiallight rays (T), and the gray graphs represent radial light rays (R). Outof the tangential light rays (T) and the radial light rays (R), thesolid lines represent the light flux F1, the longest-line-segment brokenlines represent the light flux F2, the long-line-segment broken linesrepresent the light flux F3, and the broken lines represent the lightflux F4. The projection system 3A according to the present exampleprovides high resolution, as shown in FIG. 5 .

Example 2

FIG. 6 is a light ray diagram diagrammatically showing the entireprojection system according to Example 2. FIG. 6 diagrammatically showsthe light fluxes F1 to F4, which exit out of a projection system 3Baccording to the present example and reach the screen S. The light fluxF1 is a light flux that reaches a smallest image height position. Thelight flux F4 is a light flux that reaches a largest image heightposition. The light fluxes F2 and F3 are light fluxes that reachpositions between the position that the light flux F1 reaches and theposition that the light flux F4 reaches. FIG. 7 is a light ray diagramof the projection system 3B according to Example 2. FIG. 8 is a lightray diagram of the second optical system 32 in Example 2.

The projection system according to Example 2 is based on the projectionsystem according to Example 1, and the first optical system in Example 2includes first and second deflectors that deflect the optical path ofthe first optical system. The projection system 3B according to thepresent example includes the first optical system 31 and the secondoptical system 32 sequentially arranged from the reduction side towardthe enlargement side, as shown in FIG. 6 . The first optical system 31is a refractive optical system including a plurality of lenses. Thesecond optical system 32 includes the optical element 33 and thereflector 34. The optical element 33 has the reflection surface 41, thefirst transmissive surface 42, and the second transmissive surface 43.The reflector 34 is a flat mirror. In the second optical system 32, thereflection surface 41, the reflector 34, the first transmissive surface42, and the second transmissive surface 43 are located in the presentedorder along the light traveling direction from the reduction side towardthe enlargement side.

The liquid crystal panels 18 of the image formation section 2 aredisposed in the reduction-side image formation plane of the projectionsystem 3B. The liquid crystal panels 18 form the projection images atone side of the first optical axis N of the first optical system 31 in aplane perpendicular to the first optical axis N. The screen S isdisposed in the enlargement-side image formation plane of the projectionsystem. The intermediate image 35 conjugate with the reduction-sideimage formation plane is formed between the first optical system 31 andthe reflection surface 41 of the optical element 33. The intermediateimage 35 is conjugate also with the enlargement-side image formationplane. The intermediate image 35 is formed at the side opposite thescreen S with respect to the first optical axis N of the first opticalsystem 31.

The first optical axis N of the first optical system 31 extends in theaxis-Z direction in the present example. FIGS. 6, 7, and 8 are each alight ray diagram in the plane YZ. The liquid crystal panels 18 form theprojection images at the upper side Y1 of the first optical axis N ofthe first optical system 31. The intermediate image 35 is formed at thelower side Y2 of the first optical axis N of the first optical system31. The screen S is disposed at the upper side Y1 of the first opticalaxis N of the first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15lenses L1 to L15, as shown in FIG. 7 . The lenses L1 to L15 are arrangedin the presented order from the reduction side toward the enlargementside. In the present example, the lenses L2 and L3 are bonded to eachother into the first doublet L21. The lenses L4 and L5 are bonded toeach other into the second doublet L22. The lenses L11 and L12 arebonded to each other into the third doublet L23. The lenses L13 and L14are bonded to each other into the fourth doublet L24. The aperture O isdisposed between the lens L8 and the lens L9.

The first optical system 31 includes the first deflector 38 and thesecond deflector 39, which deflect the optical path of the first opticalsystem 31. The first deflector 38 and the second deflector 39 are each aflat mirror. The first deflector 38 is disposed adjacent to and at thereduction side of the aperture O. That is, the first deflector 38 isdisposed between the lens L7 and the lens L8. The second deflector 39 isshifted from the aperture O toward the enlargement side. That is, thesecond deflector 39 is disposed between the lens L10 and the lens L11.The first optical axis N of the first optical system 31 is divided intoa first section N1 of the first optical axis that is the section at thereduction side of the first deflector 38, a second section N2 of thefirst optical axis that is the section at the enlargement side of thefirst deflector 38 but up to the second deflector 39, and a thirdsection N3 of the first optical axis that is the section at theenlargement side of the second deflector 39, and the angle between thefirst section N1 of the first optical axis and the second section N2 ofthe first optical axis is 90°. The angle between the second section N2of the first optical axis and the third section N3 of the first opticalaxis is 90°. The first section N1 of the first optical axis and thethird section N3 of the first optical axis are parallel to each other.In the present example, the first section N1 of the first optical axisand the third section N3 of the first optical axis extend in parallel toeach other.

That is, the first deflector 38 is so disposed as to incline by 45° withrespect to the first section N1 of the first optical axis and deflectsthe light flux in the first optical system 31 by 90° toward the upperside Y1. The second deflector 39 is so disposed as to incline by 45°with respect to the second section N2 of the first optical axis anddeflects back the light flux in the first optical system 31 by 180°.

The optical element 33 includes the meniscus lens 36, which has a convexshape at the enlargement side, and the reflection coating layer 37,which is provided on part of the reduction-side surface of the meniscuslens 36. The reflection surface 41 of the optical element 33 is thereflection coating layer 37. The optical element 33 is designed by usingthe second optical axis M of the reflection surface 41 as the axis inthe design stage. In other words, the second optical axis M is thedesign-stage optical axis of the reflection surface 41, the firsttransmissive surface 42, and the second transmissive surface 43. Thesecond optical axis M of the reflection surface 41 coincides with thefirst optical axis N of the first optical system 31. The second opticalaxis M of the reflection surface 41 coincides with the third section N3of the first optical axis N of the first optical system 31, as shown inFIG. 8 . The second optical axis M of the reflection surface 41therefore extends along the axis Z. The reflection surface 41 is locatedat the lower side Y2 of the second optical axis M. The firsttransmissive surface 42 and the second transmissive surface 43 arelocated at the upper side Y1 of the second optical axis M. Thereflection surface 41, the first transmissive surface 42, and the secondtransmissive surface 43 of the optical element 33 are each an asphericsurface. The aspheric surfaces are each a free-form surface in somecases. Also in this case, the free-form surfaces are designed by usingthe second optical axis M as the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of thereflection surface 41. The reflector 34 is located at the upper side Y1of the second optical axis M of the reflection surface 41. The reflector34 is shifted from the optical element 33 toward the first opticalsystem 31 in the direction along the second optical axis M of thereflection surface 41.

The pupil P of the second optical system 32 is located inside the secondoptical system 32. The pupil P of the second optical system 32 in theplane YZ is defined by the line that connects the upper intersection 53,where the upper peripheral light ray 51 a of the upper end light flux 51passing through the axis-Y-direction upper end of the effective lightray range of the second transmissive surface 43 and the upper peripherallight ray 52 a of the lower end light flux 52 passing through theaxis-Y-direction lower end of the effective light ray range 50 intersecteach other in the plane YZ, to the lower intersection 54, where thelower peripheral light ray 51 b of the upper end light flux 51 and thelower peripheral light ray 52 b of the lower end light flux 52 intersecteach other in the plane YZ. The pupil P is formed between the reflector34 and the second transmissive surface 43. The pupil P inclines withrespect to the imaginary vertical line V perpendicular to the secondoptical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3B are listed below. Thesurfaces of the lenses are numbered sequentially from the reduction sidetoward the enlargement side. Reference characters are given to thelenses, the first deflector, the second deflector, the reflectionsurface, the reflector, the first transmissive surface, and the secondtransmissive surface. Data labeled with a surface number that does notcorrespond to any of the lenses, the first deflector, the seconddeflector, the reflection surface, the reflector, the first transmissivesurface, and the second transmissive surface is dummy data. Referencecharacter R denotes the radius of curvature. Reference character Ddenotes the axial inter-surface distance. Reference character C denotesthe aperture radius. Reference characters R, D, and C are each expressedin millimeters.

Reference Surface Refraction/ character number Shape R D Glass materialreflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity25.9100 SBSL7_OHARA Refraction 13.1294 3 Spherical Infinity 0.2000Refraction 15.6811 L1 4 Spherical 28.2094 8.9572 463480.6806 Refraction16.5145 5 Spherical −83.1544 0.2000 Refraction 16.2563 L2 6 Spherical33.5314 6.6630 453456.8225 Refraction 14.7095 L3 7 Spherical 78.14781.2000 2.0010:29.132 Refraction 14.0000 8 Spherical 29.7884 0.2000Refraction 13.4642 L4 9 Spherical 28.1457 9.6926 469236.8323 Refraction13.6582 L5 10 Spherical −22.5231 1.2000 2.0009:29.135 Refraction 13.713611 Spherical −186.9823 0.2000 Refraction 14.8724 L6 12 Aspheric 48.96043.0063 441964.8821 Refraction 16.1663 13 Aspheric 314.2727 0.2000Refraction 16.3015 L7 14 Spherical 81.4934 6.3039 469050.7791 Refraction16.5299 15 Spherical −55.3604 19.1151 Refraction 16.7970 O 16 SphericalInfinity 0.0000 Reflection 26.4292 17 Spherical Infinity −19.1151Refraction 17.8529 18 Spherical Infinity −0.2000 Refraction 19.1152 L819 Spherical −61.1427 −6.0716 2.0015:19.408 Refraction 19.3498 20Spherical 196.5322 −0.8207 Refraction 19.0863 21 Spherical Infinity−18.2327 Refraction 18.3967 L9 22 Aspheric 27.0027 −1.6345 2.0027:19.317Refraction 16.8350 23 Aspheric 187.7066 −0.2000 Refraction 18.3329 L1024 Spherical 75.7408 −10.1959 590410.3496 Refraction 20.2617 25Spherical 42.1350 −22.3002 Refraction 20.7008 26 Spherical Infinity0.0000 Reflection 29.5422 27 Spherical Infinity 22.3002 Refraction21.4652 L11 28 Spherical 35.1039 12.8742 437001.951 Refraction 22.3001L12 29 Spherical −189.1707 3.8133 2.0010:29.134 Refraction 21.5043 30Spherical 43.8798 0.2000 Refraction 20.3055 L13 31 Spherical 34.229117.9986 437001.951 Refraction 21.1074 L14 32 Spherical −85.4978 8.4736792469.4538 Refraction 20.6876 33 Spherical 57.3732 9.8162 Refraction20.8208 L15 34 Aspheric −226.8989 6.3040 ‘Z-E48R’ Refraction 21.3828 35Aspheric −485.2593 0.2000 Refraction 22.3000 36 Spherical Infinity1.5000 Refraction 26.7876 37 Spherical Infinity 40.2264 Refraction27.6086 41 38 Aspheric −35.1906 0.0000 Reflection 38.8998 39 SphericalInfinity −40.2264 Refraction 74.5214 34 40 Spherical Infinity 0.0000Reflection 30.0529 41 Spherical Infinity 40.2264 Refraction 30.0529 42Spherical Infinity 0.0000 Refraction 107.4634 43 Aspheric −28.72131.2000 ‘Z-E48R’ Refraction 39.8330 43 44 Aspheric −42.6321 0.0000Refraction 54.0576 45 Spherical Infinity 439.4195 Refraction 144.9591 S46 Spherical Infinity 0.0000 Refraction 1488.5481

The aspheric coefficients of each of the aspheric surfaces are listedbelow.

Surface number S12 S13 S22 Radius of 48.96044013 314.2727343 27.00272101curvature in axis-Y direction Conic constant  1.568  −1.3 −1 (k)Fourth-order −1.02602E−05   3.23749E−06 −7.77232E−07 coefficient (A)Sixth-order  2.22500E−08   2.10974E−08 −2.87978E−09 coefficient (B)Eighth-order −4.11479E−11  −4.06491E−11 −3.62426E−12 coefficient (C)Tenth-order  2.28527E−13   2.41451E−13 coefficient (D) Twelfth-ordercoefficient (E) Fourteenth-order coefficient (F)

Surface number S23 S34 S35 Radius of 187.7066332 −226.8988513−485.2592728 curvature in axis-Y direction Conic constant  −0.88    90   0 (k) Fourth-order  −7.79758E−06  −4.00626E−05  −7.89993E−05coefficient (A) Sixth-order  1.61670E−09    1.42410E−07    2.15938E−07coefficient (B) Eighth-order  −2.71849E−12  −3.51878E−10  −4.26635E−10coefficient (C) Tenth-order    5.84931E−13    5.81509E−13 coefficient(D) Twelfth-order  −7.00335E−16  −6.28266E−16 coefficient (E)Fourteenth-order    4.42366E−19    3.57966E−19 coefficient (F)

Surface number S38 S43 S44 Radius of −35.19059003 −28.72125677−42.63205393 curvature in axis-Y direction Conic constant  −1.65124531 −2.48275343  −0.82812574 (k) Fourth-order  −1.44803E−07  −6.52555E−06   1.63369E−06 coefficient (A) Sixth-order  −3.34034E−10  −2.02478E−09 −1.36041E−10 coefficient (B) Eighth-order    1.23576E−13    2.29963E−12 −4.47648E−14 coefficient (C) Tenth-order  −5.90820E−17    3.72271E−17coefficient (D) Twelfth-order    8.23282E−21  −3.16121E−19 coefficient(E) Fourteenth-order  −5.47662E−25  −7.45167E−23 coefficient (F)

The maximum object height, the numerical aperture, the mirror radius,the lens overall length, and TR of the projection system 3B are asfollows: The maximum object height is the dimension from the firstoptical axis N of the projection system 3B to the farthest pointtherefrom in the image formation region of the surface of each of theliquid crystal panels 18. The maximum object height is expressed inmillimeters. The numerical aperture is abbreviated to NA. The mirrorradius is the radius of the first reflection surface in millimeters. Thefinal lens radius is the lens radius of the second transmissive surfacein millimeters. The lens overall length of the projection system 3B isthe distance in millimeters from the liquid crystal panels 18 to thesecond transmissive surface in the axis-Z direction. TR stands for thethrow ratio and is the quotient of the operation of dividing theprojection distance by the axis-X-direction dimension of a projectionimage projected on the screen S.

Maximum object height 11.7 NA 0.3125 Mirror radius 38.9 Final lensradius 54.1 Lens overall length 295 TR (0.59″ WXGA) 0.270

Effects and Advantages

The projection system according to the present example can provide thesame effects and advantages as those provided by the projection systemaccording to Example 1. In the present example, in which the first andsecond deflectors are provided, the optical path of the first opticalsystem is deflected back. The area occupied by the first optical systemcan therefore be reduced when viewed along the axis-Y direction, thatis, when taken along the plane XZ.

FIG. 9 shows the enlargement-side MTF of the projection system 3B. Theprojection system 3B according to the present example provides highresolution, as shown in FIG. 9 .

Example 3

FIG. 10 is a light ray diagram diagrammatically showing the entirety ofa projection system 3C according to Example 3. FIG. 10 diagrammaticallyshows the light fluxes F1 to F4, which exit out of the projection system3C according to the present example and reach the screen S. The lightflux F1 is a light flux that reaches a smallest image height position.The light flux F4 is a light flux that reaches a largest image heightposition. The light fluxes F2 and F3 are light fluxes that reachpositions between the position that the light flux F1 reaches and theposition that the light flux F4 reaches. FIG. 11 is a light ray diagramof the projection system 3C according to Example 3. FIG. 12 is a lightray diagram of the second optical system.

The projection system 3C according to the present example includes thefirst optical system 31 and the second optical system 32 sequentiallyarranged from the reduction side toward the enlargement side, as shownin FIG. 11 . The first optical system 31 is a refractive optical systemincluding a plurality of lenses. The second optical system 32 includesthe optical element 33 and the reflector 34. The optical element 33 hasa light-incident-side transmissive surface 44, the reflection surface41, the first transmissive surface 42, and the second transmissivesurface 43. The reflector 34 is a flat mirror. In the second opticalsystem 32, the light-incident-side transmissive surface 44, thereflection surface 41, the light-incident-side transmissive surface 44,the reflector 34, the first transmissive surface 42, and the secondtransmissive surface 43 are located in the presented order along thelight traveling direction from the reduction side toward the enlargementside.

The liquid crystal panels 18 of the image formation section 2 aredisposed in the reduction-side image formation plane of the projectionsystem 3C. The liquid crystal panels 18 form the projection images atone side of the first optical axis N of the first optical system 31 in aplane perpendicular to the first optical axis N. The screen S isdisposed in the enlargement-side image formation plane of the projectionsystem. The intermediate image 35 conjugate with the reduction-sideimage formation plane is formed between the first optical system 31 andthe reflection surface 41 of the optical element 33. The intermediateimage 35 is conjugate also with the enlargement-side image formationplane. The intermediate image 35 is formed at the side opposite thescreen S with respect to the first optical axis N of the first opticalsystem 31.

The first optical axis N of the first optical system 31 extends in theaxis-Z direction in the present example. FIGS. 10, 11, and 12 are each alight ray diagram in the plane YZ. The liquid crystal panels 18 form theprojection images at the upper side Y1 of the first optical axis N ofthe first optical system 31. The intermediate image 35 is formed at thelower side Y2 of the first optical axis N of the first optical system31. The screen S is disposed at the upper side Y1 of the first opticalaxis N of the first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15lenses L1 to L15, as shown in FIG. 11 . The lenses L1 to L15 arearranged in the presented order from the reduction side toward theenlargement side. In the present example, the lenses L2 and L3 arebonded to each other into the first doublet L21. The lenses L4 and L5are bonded to each other into the second doublet L22. The lenses L11 andL12 are bonded to each other into the third doublet L23. The lenses L13and L14 are bonded to each other into the fourth doublet L24. Theaperture O is disposed between the lens L7 and the lens L8.

The optical element 33 includes the meniscus lens 36, which has a convexshape at the enlargement side, and the reflection coating layer 37,which is provided on part of the enlargement-side surface of themeniscus lens 36. The reflection surface 41 of the optical element 33 isthe reflection coating layer 37. The optical element 33 is designed byusing the second optical axis M of the reflection surface 41 as the axisin the design stage. In other words, the second optical axis M is thedesign-stage optical axis of the light-incident-side transmissivesurface 44, the reflection surface 41, the first transmissive surface42, and the second transmissive surface 43. The second optical axis M ofthe reflection surface 41 coincides with the first optical axis N of thefirst optical system 31, as shown in FIG. 12 . The second optical axis Mof the reflection surface 41 therefore extends along the axis Z. Thelight-incident-side transmissive surface 44 and the reflection surface41 are located at the lower side Y2 of the second optical axis M. Thefirst transmissive surface 42 and the second transmissive surface 43 arelocated at the upper side Y1 of the second optical axis. Thelight-incident-side transmissive surface 44, and the reflection surface41, the first transmissive surface 42, and the second transmissivesurface 43 of the optical element 33 are each an aspheric surface. Theaspheric surfaces are each a free-form surface in some cases. Also inthis case, the free-form surfaces are designed by using the secondoptical axis M as the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of thereflection surface 41. The reflector 34 is located at the upper side Y1of the second optical axis M of the reflection surface 41. The reflector34 is shifted from the optical element 33 toward the first opticalsystem 31 in the direction along the second optical axis M of thereflection surface 41.

The pupil P of the second optical system 32 is located inside the secondoptical system 32. The pupil P of the second optical system 32 in theplane YZ is defined by the line that connects the upper intersection 53,where the upper peripheral light ray 51 a of the upper end light flux 51passing through the axis-Y-direction upper end of the effective lightray range of the second transmissive surface 43 and the upper peripherallight ray 52 a of the lower end light flux 52 passing through theaxis-Y-direction lower end of the effective light ray range 50 intersecteach other in the plane YZ, to the lower intersection 54, where thelower peripheral light ray 51 b of the upper end light flux 51 and thelower peripheral light ray 52 b of the lower end light flux 52 intersecteach other in the plane YZ. The pupil P is formed between the reflector34 and the second transmissive surface 43. The pupil P inclines withrespect to the imaginary vertical line V perpendicular to the secondoptical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3C are listed below. Thesurfaces of the lenses are numbered sequentially from the reduction sidetoward the enlargement side. Reference characters are given to thelenses, the light-incident-side projection surface, the reflectionsurface, the reflector, the first transmissive surface, and the secondtransmissive surface. Data labeled with a surface number that does notcorrespond to any of the lenses, the light-incident-side projectionsurface, the reflection surface, the reflector, the first transmissivesurface, and the second transmissive surface is dummy data. Referencecharacter R denotes the radius of curvature. Reference character Ddenotes the axial inter-surface distance. Reference character C denotesthe aperture radius. Reference characters R, D, and C are each expressedin millimeters.

Reference Surface Refraction/ character number Shape R D Glass materialreflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity25.9100 SBSL7_OHARA Refraction 13.6097 3 Spherical Infinity 0.0000Refraction 17.0021 L1 4 Spherical 41.2144 9.8241 SFPL51_OHARA Refraction17.8162 5 Spherical −43.6282 0.2000 Refraction 17.7483 L2 6 Spherical23.5357 6.2884 SFSL5_OHARA Refraction 14.9123 L3 7 Spherical 94.82721.2000 STIH6_OHARA Refraction 14.0000 8 Spherical 21.4819 0.2000Refraction 12.6277 L4 9 Spherical 19.0505 10.4909 SBSL7_OHARA Refraction12.6034 L5 10 Spherical −21.2275 1.2000 TAFD25_HOYA Refraction 12.011711 Spherical 63.5114 1.0411 Refraction 11.6290 L6 12 Aspheric 49.08841.2000 LBAL35_OHARA Refraction 11.6454 13 Aspheric 27.0575 0.2000Refraction 11.6632 L7 14 Spherical 26.8149 7.0725 SFSL5_OHARA Refraction11.9375 15 Spherical −32.5544 4.3889 Refraction 11.9390 O 16 SphericalInfinity 2.5976 Refraction 10.7320 L8 17 Spherical 45.3300 7.0474STIH53_OHARA Refraction 12.3109 18 Spherical −35.8311 0.2000 Refraction12.4566 L9 19 Aspheric −56.8046 1.5968 LLAM60_OHARA Refraction 12.329320 Aspheric 24.3773 7.4673 Refraction 12.6338 21 Spherical Infinity2.8159 Refraction 14.9857 L10 22 Spherical 33.2956 4.5985 STIM22_OHARARefraction 20.1790 23 Spherical 49.7914 17.6365 Refraction 20.0451 L1124 Spherical 45.3688 20.9746 STIM2_OHARA Refraction 26.0000 L12 25Spherical −28.7126 1.2000 STIH6_OHARA Refraction 23.5216 26 Spherical115.5270 0.2000 Refraction 24.2345 L13 27 Spherical 33.8126 15.5800STIL25_OHARA Refraction 27.3836 L14 28 Spherical 899.1542 1.2000STIH6_OHARA Refraction 26.7372 29 Spherical 42.8200 7.9678 Refraction24.3547 L15 30 Aspheric −256.9466 10.0000 ‘Z-E48R’ Refraction 24.5227 31Aspheric 76.1015 7.8140 Refraction 21.8030 32 Spherical Infinity 1.7043Refraction 21.8850 33 Spherical Infinity 26.6661 Refraction 22.7703 4434 Aspheric −53.7754 4.0174 ‘Z-E48R’ Refraction 30.1927 41 35 Aspheric−37.0708 −4.0174 ‘Z-E48R’ Reflection 31.6638 44 36 Aspheric −53.7754−26.6661 Refraction 29.5984 34 37 Spherical Infinity 0.0000 Reflection42.8206 38 Spherical Infinity 26.6606 Refraction 42.8206 39 SphericalInfinity 0.0000 Refraction 110.7647 43 40 Aspheric −61.4764 4.0174‘Z-E48R’ Refraction 43.5854 41 Aspheric −200.8496 0.0000 Refraction59.9999 42 Spherical Infinity 439.4195 Refraction 131.0019 S 43Spherical Infinity 0.0000 Refraction 1454.8316

The aspheric coefficients of each of the aspheric surfaces are listedbelow.

Surface number S12 S13 S19 S20 Radius of 49.08839049 27.05749563−56.80463531 24.37733913 curvature in axis-Y direction Conic constant 1.568 −1.3  −1 −0.88 (k) Fourth-order −1.27624E−04 −9.62452E−05 −2.35727E−05 −5.71363E−06 coefficient (A) Sixth-order  6.79968E−07 7.36058E−07  −6.95764E−09 −9.06493E−09 coefficient (B) Eighth-order−1.49344E−09 −2.04610E−09  −2.33118E−11 −1.65962E−11 coefficient (C)Tenth-order  2.18051E−12  3.01616E−12 coefficient (D) Twelfth-ordercoefficient (E) Fourteenth-order coefficient (F)

Surface number S30 S31 S34 S35 Radius of −256.9466198 76.10151145−53.77538203 −37.0707934 curvature in axis-Y direction Conic constant   90  0    1.432637618  −1 (k) Fourth-order    3.81759E−05 −2.49871E−05 −7.27509E−06    1.95126E−07 coefficient (A) Sixth-order  −2.36256E−08 1.46370E−07    1.22445E−08  −2.56458E−09 coefficient (B) Eighth-order −2.04848E−11 −2.70415E−10  −8.06489E−12    2.98409E−12 coefficient (C)Tenth-order    6.55740E−14  2.57801E−13    7.19014E−15    6.07298E−16coefficient (D) Twelfth-order  −4.72334E−17 −2.07333E−16  −8.05971E−18 −3.51995E−18 coefficient (E) Fourteenth-order    3.01373E−20 2.90536E−19    2.85331E−21    1.46175E−21 coefficient (F)

Surface number S36 S40 S41 Radius of −53.77538203 −61.47639674−200.8496205 curvature in axis-Y direction Conic constant    1.432637618 −0.946487863    8.952212348 (k) Fourth-order  −7.27509E−06 −3.81258E−06  −9.72802E−07 coefficient (A) Sixth-order    1.22445E−08   2.37350E−09    2.00223E−10 coefficient (B) Eighth-order  −8.06489E−12 −1.02258E−12  −4.09223E−14 coefficient (C) Tenth-order    7.19014E−15coefficient (D) Twelfth-order  −8.05971E−18 coefficient (E)Fourteenth-order    2.85331E−21 coefficient (F)

The maximum object height, the numerical aperture, the mirror radius,the lens overall length, and TR of the projection system 3C are asfollows: The maximum object height is the dimension from the firstoptical axis N of the projection system 3C to the farthest pointtherefrom in the image formation region of the surface of each of theliquid crystal panels 18. The maximum object height is expressed inmillimeters. The numerical aperture is abbreviated to NA. The mirrorradius is the radius of the first reflection surface in millimeters. Thefinal lens radius is the lens radius of the second transmissive surfacein millimeters. The lens overall length of the projection system 3C isthe distance in millimeters from the liquid crystal panels 18 to thesecond transmissive surface in the axis-Z direction. TR stands for thethrow ratio and is the quotient of the operation of dividing theprojection distance by the axis-X-direction dimension of a projectionimage projected on the screen S.

Maximum object height 11.7 NA 0.3125 Mirror radius 31.7 Final lensradius 60.0 Lens overall length 220 TR (0.59″ WXGA) 0.27

Effects and Advantages

The projection system according to the present example can provide thesame effects and advantages as those provided by the projection systemaccording to Example 1.

In the present example, the light-incident-side transmissive surface 44can refract the light flux incident on the reflection surface 41 and thelight flux reflected off the reflection surface 41 in the second opticalsystem 32. The projection distance of the projection system cantherefore be further shortened as compared with the case where thesecond optical system 32 has the first transmissive surface 42 and thesecond transmissive surface 43.

Since the light-incident-side transmissive surface 44, which is locatedat the enlargement side of the intermediate image 35, is an asphericsurface, occurrence of aberrations is readily suppressed in theenlargement-side image formation plane.

FIG. 13 shows the enlargement-side MTF of the projection system 3C. Theprojection system 3C according to the present example provides highresolution, as shown in FIG. 13 .

Example 4

FIG. 14 is a light ray diagram diagrammatically showing the entirety ofa projection system 3D according to Example 4. FIG. 14 diagrammaticallyshows the light fluxes F1 to F4, which exit out of the projection system3D according to the present example and reach the screen S. The lightflux F1 is a light flux that reaches a smallest image height position.The light flux F4 is a light flux that reaches a largest image heightposition. The light fluxes F2 and F3 are light fluxes that reachpositions between the position that the light flux F1 reaches and theposition that the light flux F4 reaches. FIG. 15 is a light ray diagramof the projection system 3D according to Example 4. FIG. 16 is a lightray diagram of the second optical system in Example 4.

The projection system according to Example 4 is based on the projectionsystem according to Example 3, and the first optical system in Example 4includes first and second deflectors that deflect the optical path ofthe first optical system. The projection system 3D according to thepresent example includes the first optical system 31 and the secondoptical system 32 sequentially arranged from the reduction side towardthe enlargement side, as shown in FIG. 15 . The first optical system 31is a refractive optical system including a plurality of lenses. Thesecond optical system 32 includes the optical element 33 and thereflector 34. The optical element 33 has the light-incident-sidetransmissive surface 44, the reflection surface 41, the firsttransmissive surface 42, and the second transmissive surface 43. Thereflector 34 is a flat mirror. In the second optical system 32, thelight-incident-side transmissive surface 44, the reflection surface 41,the light-incident-side transmissive surface 44, the reflector 34, thefirst transmissive surface 42, and the second transmissive surface 43are located in the presented order along the light traveling directionfrom the reduction side toward the enlargement side.

The liquid crystal panels 18 of the image formation section 2 aredisposed in the reduction-side image formation plane of the projectionsystem 3D. The liquid crystal panels 18 form the projection images atone side of the first optical axis N of the first optical system 31 in aplane perpendicular to the first optical axis N. The screen S isdisposed in the enlargement-side image formation plane of the projectionsystem. The intermediate image 35 conjugate with the reduction-sideimage formation plane is formed between the first optical system 31 andthe reflection surface 41 of the optical element 33. The intermediateimage 35 is conjugate also with the enlargement-side image formationplane. The intermediate image 35 is formed at the side opposite thescreen S with respect to the first optical axis N of the first opticalsystem 31.

The first optical axis N of the first optical system 31 extends in theaxis-Z direction in the present example. FIGS. 14, 15, and 16 are each alight ray diagram in the plane YZ. The liquid crystal panels 18 form theprojection images at the upper side Y1 of the first optical axis N ofthe first optical system 31. The intermediate image 35 is formed at thelower side Y2 of the first optical axis N of the first optical system31. The screen S is disposed at the upper side Y1 of the first opticalaxis N of the first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15lenses L1 to L15, as shown in FIG. 15 . The lenses L1 to L15 arearranged in the presented order from the reduction side toward theenlargement side. In the present example, the lenses L2 and L3 arebonded to each other into the first doublet L21. The lenses L4 and L5are bonded to each other into the second doublet L22. The lenses L11 andL12 are bonded to each other into the third doublet L23. The lenses L13and L14 are bonded to each other into the fourth doublet L24. Theaperture O is disposed between the lens L8 and the lens L9.

The first optical system 31 includes the first deflector 38 and thesecond deflector 39, which deflect the optical path of the first opticalsystem 31. The first deflector 38 and the second deflector 39 are each aflat mirror. The first deflector 38 is disposed adjacent to and at thereduction side of the aperture O. That is, the first deflector 38 isdisposed between the lens L7 and the lens L8. The second deflector 39 isshifted from the aperture O toward the enlargement side. That is, thesecond deflector 39 is disposed between the lens L10 and the lens L11.The first optical axis N of the first optical system 31 is divided intothe first section N1 of the first optical axis that is the section atthe reduction side of the first deflector 38, the second section N2 ofthe first optical axis that is the section at the enlargement side ofthe first deflector 38 but up to the second deflector 39, and the thirdsection N3 of the first optical axis that is the section at theenlargement side of the second deflector 39, and the angle between thefirst section N1 of the first optical axis and the second section N2 ofthe first optical axis is 90°. The angle between the second section N2of the first optical axis and the third section N3 of the first opticalaxis is 90°. The first section N1 of the first optical axis and thethird section N3 of the first optical axis are parallel to each other.In the present example, the first section N1 of the first optical axisand the third section N3 of the first optical axis extend in parallel toeach other.

That is, the first deflector 38 is so disposed as to incline by 45° withrespect to the first section N1 of the first optical axis and deflectsthe light flux in the first optical system 31 by 90° toward the upperside Y1. The second deflector 39 is so disposed as to incline by 45°with respect to the second section N2 of the first optical axis anddeflects back the light flux in the first optical system 31 by 180°.

The optical element 33 includes the meniscus lens 36, which has a convexshape at the enlargement side, and the reflection coating layer 37,which is provided on part of the enlargement-side surface of themeniscus lens 36. The reflection surface 41 of the optical element 33 isthe reflection coating layer 37. The optical element 33 is designed byusing the second optical axis M of the reflection surface 41 as the axisin the design stage. In other words, the second optical axis M is thedesign-stage optical axis of the light-incident-side transmissivesurface 44, the reflection surface 41, the first transmissive surface42, and the second transmissive surface 43. The second optical axis M ofthe reflection surface 41 coincides with the third section N3 of thefirst optical axis N of the first optical system 31, as shown in FIG. 16. The second optical axis M of the reflection surface 41 thereforeextends along the axis Z. The light-incident-side transmissive surface44 and the reflection surface 41 are located at the lower side Y2 of thesecond optical axis M. The first transmissive surface 42 and the secondtransmissive surface 43 are located at the upper side Y1 of the secondoptical axis M. The light-incident-side transmissive surface 44, thereflection surface 41, the first transmissive surface 42, and the secondtransmissive surface 43 of the optical element 33 are each an asphericsurface. The aspheric surfaces are each a free-form surface in somecases. Also in this case, the free-form surfaces are designed by usingthe second optical axis M as the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of thereflection surface 41. The reflector 34 is located at the upper side Y1of the second optical axis M of the reflection surface 41. The reflector34 is shifted from the optical element 33 toward the first opticalsystem 31 in the direction along the second optical axis M of thereflection surface 41.

The pupil P of the second optical system 32 is located inside the secondoptical system 32. The pupil P of the second optical system 32 in theplane YZ is defined by the line that connects the upper intersection 53,where the upper peripheral light ray 51 a of the upper end light flux 51passing through the axis-Y-direction upper end of the effective lightray range of the second transmissive surface 43 and the upper peripherallight ray 52 a of the lower end light flux 52 passing through theaxis-Y-direction lower end of the effective light ray range 50 intersecteach other in the plane YZ, to the lower intersection 54, where thelower peripheral light ray 51 b of the upper end light flux 51 and thelower peripheral light ray 52 b of the lower end light flux 52 intersecteach other in the plane YZ. The pupil P is formed between the reflector34 and the second transmissive surface 43. The pupil P inclines withrespect to the imaginary vertical line V perpendicular to the secondoptical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3D are listed below. Thesurfaces of the lenses are numbered sequentially from the reduction sidetoward the enlargement side. Reference characters are given to thelenses, the first deflector, the second deflector, thelight-incident-side projection surface, the reflection surface, thereflector, the first transmissive surface, and the second transmissivesurface. Data labeled with a surface number that does not correspond toany of the lenses, the first deflector, the second deflector, thelight-incident-side projection surface, the reflection surface, thereflector, the first transmissive surface, and the second transmissivesurface is dummy data. Reference character R denotes the radius ofcurvature. Reference character D denotes the axial inter-surfacedistance. Reference character C denotes the aperture radius. Referencecharacters R, D, and C are each expressed in millimeters.

Reference Surface Refraction/ character number Shape R D Glass materialreflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity25.9100 SBSL7_OHARA Refraction 13.1866 3 Spherical Infinity 0.2000Refraction 15.8391 L1 4 Spherical 60.8192 8.3858 447472.8179 Refraction16.2149 5 Spherical −33.6543 0.2000 Refraction 16.2525 L2 6 Spherical42.1742 6.8398 449655.8302 Refraction 14.5611 L3 7 Spherical −44.75011.2000 2.0010:29.134 Refraction 14.0000 8 Spherical 43.1052 0.2000Refraction 13.8696 L4 9 Spherical 31.6779 10.8169 447567.8304 Refraction14.3070 L5 10 Spherical −21.9104 1.2000 2.0010:28.886 Refraction 14.393111 Spherical −58.3816 0.2000 Refraction 15.5371 L6 12 Aspheric 96.32613.0000 878827.3593 Refraction 16.3816 13 Aspheric 60.9753 0.2000Refraction 16.4506 L7 14 Spherical 47.0513 9.2823 449491.8071 Refraction16.8655 15 Spherical −47.2067 20.0299 Refraction 17.1995 O 16 SphericalInfinity 0.0000 Reflection 27.4865 17 Spherical Infinity −20.0299Refraction 18.5462 18 Spherical Infinity −0.2000 Refraction 20.0401 L819 Spherical 57.0398 −5.8695 2.0027:19.317 Refraction 20.3345 20Spherical 1094.6879 −1.8973 Refraction 20.0379 21 Spherical Infinity−19.0977 Refraction 19.3260 L9 22 Aspheric 50.6705 −1.2000 2.0027:19.317Refraction 17.6192 23 Aspheric −202.8274 −0.2000 Refraction 18.2801 L1024 Spherical −51.6804 −8.0027 652914.3585 Refraction 19.7819 25Spherical 91.1078 −20.8653 Refraction 19.9676 26 Spherical Infinity0.0000 Reflection 28.3233 27 Spherical Infinity 20.8653 Refraction20.4211 L11 28 Spherical 38.7604 12.4568 614216.3226 Refraction 20.9520L12 29 Spherical −45.7966 3.0000 2.0027:19.317 Refraction 20.6415 30Spherical 47.4799 10.4635 Refraction 19.8139 L13 31 Spherical −92.56863.3996 611216.3189 Refraction 21.2199 L14 32 Spherical −56.0227 6.0607675797.2751 Refraction 21.7046 33 Spherical −33.7704 0.2000 Refraction22.3552 L15 34 Aspheric −243.3783 2.8440 ‘Z-E48R’ Refraction 22.3333 35Aspheric 25.0399 9.7794 Refraction 20.3862 36 Spherical Infinity 1.5030Refraction 20.4862 37 Spherical Infinity 26.6612 Refraction 21.1335 4438 Aspheric −68.3577 4.2395 ‘Z-E48R’ Refraction 28.3267 41 39 Aspheric−38.4885 −4.2395 ‘Z-E48R’ Reflection 29.5616 44 40 Aspheric −68.3577−26.6612 Refraction 27.6155 34 41 Spherical Infinity 0.0000 Reflection33.2362 42 Spherical Infinity 26.6613 Refraction 33.2362 43 SphericalInfinity 0.0000 Refraction 92.9510 42 44 Aspheric −49.2660 4.2395‘Z-E48R’ Refraction 37.4399 43 45 Aspheric −147.0473 0.0000 Refraction54.3569 46 Spherical Infinity 439.4195 Refraction 120.3501 S 47Spherical Infinity 0.0000 Refraction 1458.6948

The aspheric coefficients of each of the aspheric surfaces are listedbelow.

Surface number S12 S13 S22 S23 Radius of 96.3260961 60.9752844650.67048364 −202.8273751 curvature in axis-Y direction Conic constant 1.568 −1.3 −1  −0.88 (k) Fourth-order −1.00271E−05 −7.79867E−06−7.72183E−07  −5.91829E−06 coefficient (A) Sixth-order  3.47797E−08 3.65406E−08  2.19648E−09    2.49647E−09 coefficient (B) Eighth-order−1.44942E−11 −2.65355E−11 −3.76843E−12  −3.70003E−12 coefficient (C)Tenth-order  5.15470E−15  2.45256E−14 coefficient (D) Twelfth-ordercoefficient (E) Fourteenth-order coefficient (F)

Surface number S34 S35 S38 S39 Radius of −243.3783218 25.03986207−68.35771811 −38.48848791 curvature in axis-Y direction Conic constant   90  0    3.309513291  −1 (k) Fourth-order    2.59808E−05 −3.57184E−05 −9.53327E−06    5.03313E−07 coefficient (A) Sixth-order    4.74275E−08 1.85049E−07    1.28167E−08  −5.25830E−09 coefficient (B) Eighth-order −3.01496E−10 −5.17448E−10  −1.14594E−11    8.21603E−12 coefficient (C)Tenth-order    6.68588E−13  5.85946E−13    1.49774E−14  −5.49356E−15coefficient (D) Twelfth-order  −7.34682E−16 −4.18133E−16  −1.53274E−17   4.32667E−19 coefficient (E) Fourteenth-order    4.02340E−19 4.30864E−19    5.55757E−21    3.62088E−22 coefficient (F)

Surface number S40 S44 S45 Radius of −68.35771811 −49.26602456−147.047343 curvature in axis-Y direction Conic constant    3.309513291−13.20511972    5.099781969 (k) Fourth-order  −9.53327E−06  −1.27110E−05 −8.98450E−07 coefficient (A) Sixth-order    1.28167E−08    7.61054E−09   1.15337E−10 coefficient (B) Eighth-order  −1.14594E−11  −3.45915E−12 −3.33257E−14 coefficient (C) Tenth-order    1.49774E−14 coefficient (D)Twelfth-order  −1.53274E−17 coefficient (E) Fourteenth-order   5.55757E−21 coefficient (F)

The maximum object height, the numerical aperture, the mirror radius,the lens overall length, and TR of the projection system 3D are asfollows: The maximum object height is the dimension from the firstoptical axis N of the projection system 3D to the farthest pointtherefrom in the image formation region of the surface of each of theliquid crystal panels 18. The maximum object height is expressed inmillimeters. The numerical aperture is abbreviated to NA. The mirrorradius is the radius of the first reflection surface in millimeters. Thefinal lens radius is the lens radius of the second transmissive surfacein millimeters. The lens overall length of the projection system 3D isthe distance in millimeters from the liquid crystal panels 18 to thesecond transmissive surface in the axis-Z direction. TR stands for thethrow ratio and is the quotient of the operation of dividing theprojection distance by the axis-X-direction dimension of a projectionimage projected on the screen S.

Maximum object height 11.7 NA 0.3125 Mirror radius 29.6 Final lensradius 54.4 Lens overall length 276 TR (0.59″ WXGA) 0.275

Effects and Advantages

The projection system according to the present example can provide thesame effects and advantages as those provided by the projection systemaccording to Example 3. In the present example, in which the first andsecond deflectors are provided, the optical path of the first opticalsystem is deflected back. The area occupied by the first optical systemcan therefore be reduced when viewed along the axis-Y direction.

FIG. 17 shows the enlargement-side MTF of the projection system 3D. Theprojection system 3D according to the present example provides highresolution, as shown in FIG. 17 .

Example 5

FIG. 18 is a light ray diagram diagrammatically showing the entirety ofa projection system 3E according to Example 5. FIG. 18 diagrammaticallyshows the light fluxes F1 to F4, which exit out of the projection system3E according to the present example and reach the screen S. The lightflux F1 is a light flux that reaches a smallest image height position.The light flux F4 is a light flux that reaches a largest image heightposition. The light fluxes F2 and F3 are light fluxes that reachpositions between the position that the light flux F1 reaches and theposition that the light flux F4 reaches. FIG. 19 is a light ray diagramof the projection system 3E according to Example 5. FIG. 20 is a lightray diagram of the second optical system in Example 5.

In the projection system according to Example 5, the first opticalsystem includes first and second deflectors that deflect the opticalpath of the first optical system, as in Example 4. The projection system3E according to the present example includes the first optical system 31and the second optical system 32 sequentially arranged from thereduction side toward the enlargement side, as shown in FIG. 19 . Thefirst optical system 31 is a refractive optical system including aplurality of lenses. The second optical system 32 includes the opticalelement 33 and the reflector 34. The optical element 33 has thelight-incident-side transmissive surface 44, the reflection surface 41,the first transmissive surface 42, and the second transmissive surface43. The reflector 34 is a flat mirror. In the second optical system 32,the light-incident-side transmissive surface 44, the reflection surface41, the light-incident-side transmissive surface 44, the reflector 34,the first transmissive surface 42, and the second transmissive surface43 are located in the presented order along the light travelingdirection from the reduction side toward the enlargement side.

The liquid crystal panels 18 of the image formation section 2 aredisposed in the reduction-side image formation plane of the projectionsystem 3E. The liquid crystal panels 18 form the projection images atone side of the first optical axis N of the first optical system 31 in aplane perpendicular to the first optical axis N. The screen S isdisposed in the enlargement-side image formation plane of the projectionsystem. The intermediate image 35 conjugate with the reduction-sideimage formation plane is formed between the first optical system 31 andthe reflection surface 41 of the optical element 33. The intermediateimage 35 is conjugate also with the enlargement-side image formationplane. The intermediate image 35 is formed at the side opposite thescreen S with respect to the first optical axis N of the first opticalsystem 31.

The first optical axis N of the first optical system 31 extends in theaxis-Z direction in the present example. FIGS. 18, 19, and 20 are each alight ray diagram in the plane YZ. The liquid crystal panels 18 form theprojection images at the upper side Y1 of the first optical axis N ofthe first optical system 31. The intermediate image 35 is formed at thelower side Y2 of the first optical axis N of the first optical system31. The screen S is disposed at the upper side Y1 of the first opticalaxis N of the first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15lenses L1 to L15, as shown in FIG. 19 . The lenses L1 to L15 arearranged in the presented order from the reduction side toward theenlargement side. In the present example, the lenses L2 and L3 arebonded to each other into the first doublet L21. The lenses L4 and L5are bonded to each other into the second doublet L22. The lenses L11 andL12 are bonded to each other into the third doublet L23. The lenses L13and L14 are bonded to each other into the fourth doublet L24. The lens15 is a lens having no portion at the upper side Y1 of the first opticalaxis N of the first optical system 31. The aperture O is disposedbetween the lens L8 and the lens L9.

The first optical system 31 includes the first deflector 38 and thesecond deflector 39, which deflect the optical path of the first opticalsystem 31. The first deflector 38 and the second deflector 39 are each aflat mirror. The first deflector 38 is disposed adjacent to and at thereduction side of the aperture O. That is, the first deflector 38 isdisposed between the lens L7 and the lens L8. The second deflector 39 isshifted from the aperture O toward the enlargement side. That is, thesecond deflector 39 is disposed between the lens L10 and the lens L11.The first optical axis N of the first optical system 31 is divided intothe first section N1 of the first optical axis that is the section atthe reduction side of the first deflector 38, the second section N2 ofthe first optical axis that is the section at the enlargement side ofthe first deflector 38 but up to the second deflector 39, and the thirdsection N3 of the first optical axis that is the section at theenlargement side of the second deflector 39, and the angle between thefirst section N1 of the first optical axis and the second section N2 ofthe first optical axis is 90°. The angle between the second section N2of the first optical axis and the third section N3 of the first opticalaxis is 90°. The first section N1 of the first optical axis and thethird section N3 of the first optical axis are parallel to each other.In the present example, the first section N1 of the first optical axisand the third section N3 of the first optical axis extend in parallel toeach other.

That is, the first deflector 38 is so disposed as to incline by 45° withrespect to the first section N1 of the first optical axis and deflectsthe optical path of the first optical system 31 by 90° toward the upperside Y1. The second deflector 39 is so disposed as to incline by 45°with respect to the second section N2 of the first optical axis anddeflects back the light path of the first optical system 31 by 180°.

The optical element 33 includes the meniscus lens 36, which has a convexshape at the enlargement side, and the reflection coating layer 37,which is provided on part of the enlargement-side surface of themeniscus lens 36. The reflection surface 41 of the optical element 33 isthe reflection coating layer 37. The optical element 33 is designed byusing the second optical axis M of the reflection surface 41 as the axisin the design stage. In other words, the second optical axis M is thedesign-stage optical axis of the light-incident-side transmissivesurface 44, the reflection surface 41, the first transmissive surface42, and the second transmissive surface 43. The second optical axis M ofthe reflection surface 41 coincides with the third section N3 of thefirst optical axis N of the first optical system 31, as shown in FIG. 20. The second optical axis M of the reflection surface 41 thereforeextends along the axis Z. The light-incident-side transmissive surface44 and the reflection surface 41 are located at the lower side Y2 of thesecond optical axis M. The first transmissive surface 42 and the secondtransmissive surface 43 are located at the upper side Y1 of the secondoptical axis M. The light-incident-side transmissive surface 44, thereflection surface 41, the first transmissive surface 42, and the secondtransmissive surface 43 of the optical element 33 are each an asphericsurface. The aspheric surfaces are each a free-form surface in somecases. Also in this case, the free-form surfaces are designed by usingthe second optical axis M as the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of thereflection surface 41. The reflector 34 is located at the upper side Y1of the second optical axis M of the reflection surface 41. The reflector34 is shifted from the optical element 33 toward the first opticalsystem 31 in the direction along the second optical axis M of thereflection surface 41. The reflector 34 and the lens L15 of the firstoptical system 31 overlap with each other when viewed in the directionperpendicular to the first optical axis N of the first optical system31.

The pupil P of the second optical system 32 is located inside the secondoptical system 32. The pupil P of the second optical system 32 in theplane YZ is defined by the line that connects the upper intersection 53,where the upper peripheral light ray 51 a of the upper end light flux 51passing through the axis-Y-direction upper end of the effective lightray range of the second transmissive surface 43 and the upper peripherallight ray 52 a of the lower end light flux 52 passing through theaxis-Y-direction lower end of the effective light ray range 50 intersecteach other in the plane YZ, to the lower intersection 54, where thelower peripheral light ray 51 b of the upper end light flux 51 and thelower peripheral light ray 52 b of the lower end light flux 52 intersecteach other in the plane YZ. The pupil P is formed between the reflector34 and the second transmissive surface 43. The pupil P inclines withrespect to the imaginary vertical line V perpendicular to the secondoptical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3E are listed below. Thesurfaces of the lenses are numbered sequentially from the reduction sidetoward the enlargement side. Reference characters are given to thelenses, the first deflector, the second deflector, thelight-incident-side projection surface, the reflection surface, thereflector, the first transmissive surface, and the second transmissivesurface. Data labeled with a surface number that does not correspond toany of the lenses, the first deflector, the second deflector, thelight-incident-side projection surface, the reflection surface, thereflector, the first transmissive surface, and the second transmissivesurface is dummy data. Reference character R denotes the radius ofcurvature. Reference character D denotes the axial inter-surfacedistance. Reference character C denotes the aperture radius. Referencecharacters R, D, and C are each expressed in millimeters.

Reference Surface Refraction/ character number Shape R D Glass materialreflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity25.9100 SBSL7_OHARA Refraction 13.1449 3 Spherical Infinity 0.2000Refraction 15.7239 L1 4 Spherical 35.4215 10.4750 443314.8653 Refraction16.3636 5 Spherical −37.0296 0.2000 Refraction 16.2009 L2 6 Spherical124.1837 6.3938 454154.8344 Refraction 14.5415 L3 7 Spherical −29.40131.2162 2.0006:28.214 Refraction 14.0000 8 Spherical 59.5041 0.2089Refraction 14.3901 L4 9 Spherical 36.6649 11.7954 444852.8471 Refraction15.1102 L5 10 Spherical −20.0854 1.2000 2.0010:29.134 Refraction 15.272811 Spherical −46.8668 0.2405 Refraction 17.0887 L6 12 Aspheric 88.27033.2943 735074.5321 Refraction 19.0117 13 Aspheric 50.5058 0.2128Refraction 19.2901 L7 14 Spherical 46.6480 11.7146 456203.7378Refraction 19.8069 15 Spherical −42.2516 21.9375 Refraction 20.2330 O 16Spherical Infinity 0.0000 Reflection 31.3716 17 Spherical Infinity−22.2165 Refraction 21.5781 18 Spherical Infinity −0.2311 Refraction22.6808 L8 19 Spherical −59.3719 −7.0715 2.0005:19.475 Refraction22.9207 20 Spherical 735.6722 −1.3341 Refraction 22.5338 21 SphericalInfinity −20.5635 Refraction 21.8161 L9 22 Aspheric 37.4859 −1.20002.0027:19.317 Refraction 19.0086 23 Aspheric 4094.4011 −2.7557Refraction 19.9946 L10 24 Spherical −75.4732 −10.6449 647255.4076Refraction 23.0115 25 Spherical 56.1392 23.6931 Refraction 23.2989 26Spherical Infinity 0.0000 Reflection 32.5119 27 Spherical Infinity23.6931 Refraction 21.7554 L11 28 Spherical 63.2789 12.7993 612767.3176Refraction 20.3041 L12 29 Spherical −30.8281 6.1889 2.0020:19.359Refraction 19.9647 30 Spherical 72.5265 13.1602 Refraction 20.7543 L1331 Spherical −61.7004 4.4566 537239.4139 Refraction 23.3612 L14 32Spherical −42.0251 6.5691 816278.2248 Refraction 24.0343 33 Spherical−31.8478 0.2000 Refraction 25.0031 L15 34 Aspheric −252.1895 10.0000‘Z-E48R’ Refraction 24.7280 35 Aspheric 28.5103 10.3567 Refraction21.9118 36 Spherical Infinity 0.0000 Refraction 22.9461 37 SphericalInfinity 33.6948 Refraction 22.9461 44 38 Aspheric −49.4134 2.8111‘Z-E48R’ Refraction 32.4428 41 39 Aspheric −34.9985 −2.8111 ‘Z-E48R’Reflection 34.7017 44 40 Aspheric −49.4134 −41.9647 Refraction 31.881434 41 Spherical Infinity 0.0000 Reflection 50.8876 42 Spherical Infinity42.0161 Refraction 50.8876 43 Spherical Infinity 0.0000 Refraction141.6424 42 44 Aspheric −46.9659 2.8111 ‘Z-E48R’ Refraction 51.5235 4345 Aspheric −50.7702 0.0000 Refraction 75.0046 46 Spherical Infinity307.4195 Refraction 217.6765 S 47 Spherical Infinity 0.0000 Refraction1488.5481

The aspheric coefficients of each of the aspheric surfaces are listedbelow.

Surface number S12 S13 S22 S23 Radius of 88.27026489 50.5058432937.48592767 4094.401136 curvature in axis-Y direction Conic constant 1.568 −1.3 −1  −0.88 (k) Fourth-order −1.10349E−05 −7.88464E−06−6.81021E−07  −5.47787E−06 coefficient (A) Sixth-order  3.44274E−08 3.49784E−08 −1.59217E−09   5.07966E−10 coefficient (B) Eighth-order−2.07712E−11 −2.99526E−11  9.85211E−14  −3.75235E−13 coefficient (C)Tenth-order  4.62378E−15  1.40174E−14 coefficient (D) Twelfth-ordercoefficient (E) Fourteenth-order coefficient (F)

Surface number S34 S35 S38 S39 Radius of −252.189464 28.51032743−49.41336502 −34.99850714 curvature in axis-Y direction Conic constant   90  0    0.758064337  −1 (k) Fourth-order    1.16695E−05 −3.05019E−05 −1.00951E−05    1.20305E−06 coefficient (A) Sixth-order    7.16140E−08 1.86410E−07    1.15029E−08  −6.10403E−09 coefficient (B) Eighth-order −3.30028E−10 −5.07229E−10  −1.20410E−11    8.66480E−12 coefficient (C)Tenth-order    6.66535E−13  6.31522E−13    1.79838E−14  −5.09972E−15coefficient (D) Twelfth-order  −6.92904E−16 −4.55829E−16  −1.41251E−17   5.89237E−19 coefficient (E) Fourteenth-order    3.10765E−19 2.04805E−19    3.33978E−21    1.92772E−22 coefficient (F)

Surface number S40 S44 S45 Radius of −49.41336502 −46.96586421−50.77015164 curvature in axis-Y direction Conic constant    0.758064337 −0.865769094  −0.687556133 (k) Fourth-order  −1.00951E−05  −6.36237E−06   2.54890E−06 coefficient (A) Sixth-order    1.15029E−08    4.35750E−09 −3.89464E−10 coefficient (B) Eighth-order  −1.20410E−11  −9.84603E−13   2.49570E−14 coefficient (C) Tenth-order    1.79838E−14 coefficient(D) Twelfth-order  −1.41251E−17 coefficient (E) Fourteenth-order   3.33978E−21 coefficient (F)

The maximum object height, the numerical aperture, the mirror radius,the lens overall length, and TR of the projection system 3E are asfollows: The maximum object height is the dimension from the firstoptical axis N of the projection system 3E to the farthest pointtherefrom in the image formation region of the surface of each of theliquid crystal panels 18. The maximum object height is expressed inmillimeters. The numerical aperture is abbreviated to NA. The mirrorradius is the radius of the first reflection surface in millimeters. Thefinal lens radius is the lens radius of the second transmissive surfacein millimeters. The lens overall length of the projection system 3E isthe distance in millimeters from the liquid crystal panels 18 to thesecond transmissive surface in the axis-Z direction. TR stands for thethrow ratio and is the quotient of the operation of dividing theprojection distance by the axis-X-direction dimension of a projectionimage projected on the screen S.

Maximum object height 11.7 NA 0.3125 Mirror radius 34.7 Final lensradius 75.1 Lens overall length 318 TR (0.59″ WXGA) 0.188

Effects and Advantages

The projection system according to the present example can provide thesame effects and advantages as those provided by the projection systemaccording to Example 4.

In the present example, the lens L15 of the first optical system 31 andthe reflector 34 overlap with each other when viewed in the directionperpendicular to the optical axis of the first optical system 31. Thefirst optical system and the second optical system therefore approacheach other in the direction of the optical axis of the first opticalsystem, whereby the size of the projection system can be reduced in theoptical axis direction.

FIG. 21 shows the enlargement-side MTF of the projection system 3E. Theprojection system 3E according to the present example provides highresolution, as shown in FIG. 21 .

What is claimed is:
 1. A projection system, in which light travels froma reduction side to an enlargement side along a light travelingdirection, comprising: a first optical system; and a second opticalsystem including an optical element and a reflector and disposed at theenlargement side of the first optical system, wherein the opticalelement has a reflection surface, a first transmissive surface disposedat the enlargement side of the reflection surface, and a secondtransmissive surface disposed at the enlargement side of the firsttransmissive surface, the reflector is disposed at the enlargement sideof the reflection surface and at the reduction side of the firsttransmissive surface, the reflector is disposed between the opticalelement and the first optical system in a direction along a firstoptical axis of the first optical system, and the reflector is a flatmirror that is perpendicular to a second optical axis of the reflectionsurface.
 2. A projection system, in which light travels from a reductionside to an enlargement side along a light traveling direction,comprising: a first optical system; and a second optical systemincluding an optical element and a reflector and disposed at theenlargement side of the first optical system, wherein the opticalelement has a light-incident-side transmissive surface, a reflectionsurface disposed at the enlargement side of the light-incident-sidetransmissive surface, a first transmissive surface disposed at theenlargement side of the reflection surface, and a second transmissivesurface disposed at the enlargement side of the first transmissivesurface, the reflector is disposed at the enlargement side of thereflection surface and at the reduction side of the first transmissivesurface, light passing through the light-incident-side transmissivesurface and reflected by the reflection surface is incident on thelight-incident-side transmissive surface again and travels toward thereflector, the reflector is disposed between the optical element and thefirst optical system in a direction along a first optical axis of thefirst optical system, and the reflector is a flat mirror that isperpendicular to a second optical axis of the reflection surface.
 3. Theprojection system according to claim 2, wherein the light-incident-sidetransmissive surface is an aspheric surface.
 4. The projection systemaccording to claim 1, wherein the reflection surface has a concaveshape.
 5. The projection system according to claim 1, wherein the secondtransmissive surface has a convex shape protruding toward theenlargement side.
 6. The projection system according to claim 1, whereinthe first transmissive surface has a convex shape protruding toward theenlargement side.
 7. The projection system according to claim 1, whereinthe reflection surface is an aspheric surface.
 8. The projection systemaccording to claim 1, wherein the second transmissive surface is anaspheric surface.
 9. The projection system according to claim 1, whereinthe first transmissive surface is an aspheric surface.
 10. Theprojection system according to claim 1, wherein the reflector includes aflat mirror.
 11. The projection system according to claim 1, wherein thereflection surface is located at one side of a second optical axis ofthe reflection surface, and the reflector, the first transmissivesurfaces, and the second transmissive surface are located at other sideof the second optical axis.
 12. The projection system according to claim2, wherein the reflection surface and the light-incident-sidetransmissive surface are located at one side of a second optical axis ofthe reflection surface, and the reflector, the first transmissivesurfaces, and the second transmissive surface are located at other sideof the second optical axis.
 13. The projection system according to claim11, wherein axes X, Y, and Z are three axes perpendicular to oneanother, an axis-X direction being a width direction of anenlargement-side image formation plane, an axis-Y direction being anupward/downward direction of the enlargement-side image formation plane,and an axis-Z direction being a direction perpendicular to theenlargement-side image formation plane, a pupil that connects an upperintersection to a lower intersection inclines with respect to animaginary vertical line perpendicular to the second optical axis in aplane YZ containing the first and second optical axes, the upperintersection is an intersection where an upper peripheral light ray ofan upper end light flux passing through an upper end of an effectivelight ray range of the second transmissive surface that is an upper endin the axis-Y direction and an upper peripheral light ray of a lower endlight flux passing through a lower end of the effective light ray rangethat is a lower end in the axis-Y direction intersect each other in theplane YZ, and the lower intersection is an intersection where a lowerperipheral light ray of the upper end light flux and a lower peripherallight ray of the lower end light flux intersect each other in the planeYZ.
 14. The projection system according to claim 1, wherein the firstoptical system includes a first deflector that deflects an optical pathof the first optical system.
 15. The projection system according toclaim 14, wherein an angle between a first section of the first opticalaxis that is a section at the reduction side of the first deflector anda second section of the first optical axis that is a section at theenlargement side of the first deflector is 90°.
 16. The projectionsystem according to claim 14, wherein the first optical system includesa second deflector that deflects the optical path toward the enlargementside of the first deflector.
 17. The projection system according toclaim 16, wherein an angle between the second section of the firstoptical axis, which is a section at the reduction side of the seconddeflector, and a third section of the first optical axis that is asection at the enlargement side of the second deflector is 90°.
 18. Theprojection system according to claim 17, wherein the first section andthe third section are parallel to each other.
 19. The projection systemaccording to claim 1, wherein an intermediate image is formed betweenthe first optical system and the reflection surface.
 20. A projectorcomprising: the projection system according to claim 1; and an imageformation section that forms a projection image in a reduction-sideimage formation plane of the projection system.